JP5007937B2 - Attenuator - Google Patents

Description

  The present invention relates to an attenuator capable of adjusting an attenuation ratio used in an oscilloscope probe or the like, and more particularly to an attenuator capable of adjusting an attenuation ratio with a simple circuit configuration.

  Prior art documents related to an attenuator capable of adjusting an attenuation ratio used in a conventional oscilloscope probe or the like include the following.

Japanese Patent Publication No. 01-013065 Japanese Patent Publication No. 01-037044 Japanese Patent Laid-Open No. 10-070438 Japanese Patent Laid-Open No. 11-258273

  FIG. 4 is a configuration circuit diagram showing an example of a conventional attenuator. In FIG. 4, 1 is a resistor, 2 is a capacitor, 3 is a variable resistor such as a trimmer resistor, 4 is a variable capacitor such as a trimmer capacitor, 100 is an input voltage signal, and 101 is an output voltage signal.

  The input voltage signal 100 is applied to one end of the resistor 1 and one end of the capacitor 2. The other end of the resistor 1 outputs an output voltage signal 101, and the other end of the capacitor 2, one end of the variable resistor 3, and the variable capacitor 4. Each is connected to one end. The other end of the variable resistor 3 and the other end of the variable capacitor 4 are grounded.

  Here, the operation of the conventional example shown in FIG. 4 will be described. The low frequency component of the input voltage signal 100 is divided by a voltage dividing circuit composed of a resistor 1 and a variable resistor 3, and the high frequency component of the input voltage signal 100 is composed of a capacitor 2 and a variable capacitor 4. Is divided by.

  For example, if the resistance value of the resistor 1 is “R1” and the resistance value of the variable resistor 3 is “R2”, the low frequency component attenuation ratio of the input voltage signal 100 is “R2 / (R1 + R2)”. If the capacitance value of the capacitor 2 is “C1” and the capacitance value of the variable capacitor 4 is “C2”, the high-frequency component attenuation ratio of the input voltage signal 100 is “C1 / (C1 + C2)”.

  When the attenuation ratio of the low frequency component of the input voltage signal 100 is equal to the attenuation ratio of the high frequency component of the input voltage signal 100, the attenuator has a flat frequency characteristic.

  For example, an attenuator having a flat frequency characteristic can be realized by designing the attenuator so that the resistance ratio and the capacitance ratio are equal, in other words, “R1 / R2 = C2 / C1”.

  However, in practice, it is difficult to equalize the resistance ratio and the capacitance ratio due to variations in circuit elements. Therefore, by adjusting the resistance value of the variable resistor 3 and the capacitance value of the variable capacitor 4, a flat frequency characteristic can be obtained. An attenuator is realized.

  FIG. 5 is a configuration circuit diagram showing another example of the conventional attenuator described in “Patent Document 3”. 5, 1 and 2 are denoted by the same reference numerals as in FIG. 4, 5 is a resistor, 6 and 9 are capacitors, 7 and 8 are variable gain amplifier circuits, 100a is an input voltage signal, 101a is an output voltage signal, Reference numerals 102 and 103 denote gain control signals.

  The input voltage signal 100a is applied to one end of the resistor 1 and one end of the capacitor 2, and the other end of the resistor 1 outputs an output voltage signal 101a, and the other end of the capacitor 2, one end of the resistor 5, and the capacitors 6 and 9 are output. One end is connected to the input terminals of the variable gain amplifier circuits 7 and 8, respectively.

  The output terminal of the variable gain amplifier circuit 7 is connected to the other end of the resistor 5, the output terminal of the variable gain amplifier circuit 8 is connected to the other end of the capacitor 9, and the other end of the capacitor 6 is grounded. Further, the gain control signals 102 and 103 are applied to the control input terminals of the variable gain amplifier circuits 7 and 8.

  Here, the operation of the conventional example shown in FIG. 5 will be described. By controlling the gain of the variable gain amplifier circuit 7 by the gain control signal 102, the equivalent resistance value of the resistor 5 is adjusted.

For example, when the resistance value of the resistor 5 is “R3” and the gain of the variable gain amplifier circuit 7 is “A1”, the equivalent resistance value “R” is
R = R3 / (1-A1) (1)
It becomes.

  On the other hand, by controlling the gain of the variable gain amplifier circuit 8 by the gain control signal 103, the equivalent capacitance values of the capacitors 6 and 9 are adjusted.

For example, when the capacitance values of the capacitors 6 and 9 are “C3” and “C4” and the gain of the variable gain amplifier circuit 8 is “A2”, the equivalent capacitance value “C” is
C = C3 + (1-A2) .C4 (2)
It becomes.

  That is, by controlling the gains of the variable gain amplifier circuits 7 and 8 by the gain control signals 102 and 103, the equivalent resistance value “R” and the equivalent capacitance value “C” can be adjusted, so that the input voltage signal 100a By adjusting the attenuation ratio of the low-frequency component and the attenuation ratio of the high-frequency component of the input voltage signal 100a, an attenuator having a flat frequency characteristic can be realized.

  However, in the conventional example shown in FIG. 4, when adjusting the frequency characteristic (attenuation ratio), it is necessary to adjust the resistance value and the capacitance value by directly contacting the variable resistor 3 (trimmer resistor) and the variable capacitor 4 (trimmer capacitor). There is.

  In this case, since the frequency characteristics, particularly the frequency characteristics of the high frequency, change due to contact with the variable resistor 3 and the variable capacitor 4, it is difficult to adjust the resistance value and the capacitance value by one adjustment operation. There was a problem.

  Also, when it is finally stored in the shield case, it cannot be contacted with the variable resistor 3 (trimmer resistor) and the variable capacitor 4 (trimmer capacitor) at the final mounting stage. After the work, there is a need to repeat the procedure of checking the frequency characteristics by storing it in the shield case again, and there is a problem that the adjustment work becomes very complicated.

Further, although the frequency characteristic (attenuation ratio) can be electrically adjusted by a gain control signal in the conventional example shown in FIG. 5, a variable gain circuit having four quadrants is required as the variable gain amplifying circuits 7 and 8. There was a problem that the circuit configuration was complicated.
Therefore, the problem to be solved by the present invention is to realize an attenuator capable of adjusting an attenuation ratio with a simple circuit configuration.

In order to achieve such a problem, the invention according to claim 1 of the present invention is:
In an attenuator with adjustable attenuation ratio,
A resistor that converts an input voltage signal into a low-frequency component current, a capacitor that converts the input voltage signal into a high-frequency component current, a load circuit in which a resistor and a capacitor are connected in parallel, the low-frequency component current, and the high-frequency component current Are provided with an attenuation ratio adjusting means for supplying the load circuit with a current obtained by adding the currents to the load circuit, and an input current value adjusting means for adjusting the current value of the low-frequency component current flowing into the attenuation ratio adjusting means. Thus, the attenuation ratio can be adjusted with a simple circuit configuration.

The invention according to claim 2
In an attenuator with adjustable attenuation ratio,
A resistor that converts an input voltage signal into a low-frequency component current, a capacitor that converts the input voltage signal into a high-frequency component current, a load circuit in which a resistor and a capacitor are connected in parallel, the low-frequency component current, and the high-frequency component current Is provided with an attenuation ratio adjusting means for supplying a current obtained by adding the currents to the load circuit and an input current value adjusting means for adjusting a current value flowing into the attenuation ratio adjusting means. The damping ratio can be adjusted with.

The invention described in claim 3
The attenuator according to claim 1 or 2,
The damping ratio adjusting means is
The low-frequency component current is supplied to the first and second constant current sources and the emitter, respectively, and connected to the first constant-current source, and the control voltage signal of the low-frequency component current is applied to the base of one transistor. The first differential circuit to be applied and the high frequency component current are respectively supplied to the emitter and connected to the second constant current source, and the control voltage signal of the high frequency component current is applied to the base of one transistor. And a third constant current source for supplying the added current to the load circuit, to which the collectors of the other transistors of the first and second differential circuits are respectively connected. As a result, the attenuation ratio can be adjusted with a simple circuit configuration.

The invention according to claim 4
The attenuator according to claim 1 or 2,
The damping ratio adjusting means is
The low-frequency component current is supplied to the first and second constant current sources and the emitter, respectively, and the first constant-current source is connected, and the control current signal of the low-frequency component current is converted into a voltage. The high frequency component current is supplied to the first differential circuit applied to the base of the transistor and the emitter, and the second constant current source is connected to convert the control current signal of the high frequency component current into a voltage. A second differential circuit applied to the base of one transistor and a collector of the other transistor of the first and second differential circuits are connected to each other, and the added current is supplied to the load circuit. By configuring with the three constant current sources, the attenuation ratio can be adjusted with a simple circuit configuration.

The invention according to claim 5
The attenuator of claim 1, wherein
The input current value adjusting means is
Consists of a constant current source, and a transistor connected to one end of the resistor for converting the input voltage signal into a low frequency component current and the constant current source to the emitter, and the emitter potential set equal to the ground potential. As a result, the attenuation ratio can be adjusted with a simple circuit configuration.

The invention described in claim 6
The attenuator according to claim 2, wherein
The input current value adjusting means is
The constant voltage source is connected to one end of the resistor for converting an input voltage signal into a low frequency component current and sets a current value flowing into the attenuation ratio adjusting means to 0 when the input voltage signal is a ground voltage. Thus, the attenuation ratio can be adjusted with a simple circuit configuration.

The present invention has the following effects.
According to the inventions of claims 1, 2, 3, 4, 5 and 6, the input voltage signal is converted into a low-frequency component current and a high-frequency component current by a resistor and a capacitor, and the low-frequency component current and the high-frequency component current are converted. Is supplied to the load circuit at a rate independent of each other, the attenuation ratio can be adjusted with a simple circuit configuration.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of an attenuator according to the present invention.

  In FIG. 1, 10 and 22 are resistors, 11 and 21 are capacitors, 13 is a PNP transistor (hereinafter simply referred to as a transistor), 15, 16, 18 and 19 are NPN transistors (hereinafter simply referred to as transistors), 12, 14, 17 and 20 are constant current sources, 100b is an input voltage signal, 101b is an output voltage signal, 104 and 105 are bias voltages, and 106 and 107 are control voltage signals.

  Reference numerals 12 and 13 constitute input current value adjusting means for low-frequency component currents, and 14, 15, 16, 17, 18, 19 and 20 constitute attenuation ratio adjusting means.

  The input voltage signal 100b is applied to one end of the resistor 10 and one end of the capacitor 11, and the other end of the resistor 10 is connected to one end of the constant current source 12 and the emitter of the transistor 13, respectively.

  The other end of the capacitor 11 is connected to the emitters of the transistors 15 and 16 and one end of the constant current source 17, respectively. The collector of the transistor 13 is connected to the emitters of the transistors 18 and 19 and one end of the constant current source 20, respectively.

  One end of the constant current source 14 outputs an output voltage signal 101 b and is connected to the collectors of the transistors 15 and 18, one end of the capacitor 21, and one end of the resistor 22.

  The bias voltage 104 is applied to the base of the transistor 13, and the bias voltage 105 is applied to the bases of the transistors 15 and 18, respectively. Control voltage signals 106 and 107 are applied to the bases of transistors 16 and 19, respectively.

  Further, the other ends of the constant current sources 12 and 14 and the collectors of the transistors 16 and 19 are connected to a positive voltage source, respectively, and the other ends of the constant current sources 17 and 20 are connected to a negative voltage source, respectively. The other end of the resistor 22 is grounded.

  Here, the operation of the embodiment shown in FIG. 1 will be described. The bias voltage 104 applied to the base of the transistor 13 is set so that the potential of the emitter of the transistor 13 is equal to the ground potential.

  Further, the bias voltage 105 having a fixed value is applied to the base of the transistor 15, and the control voltage signal 106 is supplied to the base of the transistor 16 to control the value of the current flowing through the transistor 16. It is possible to adjust the value of the current flowing through the transistors 15, in other words, the ratio of the current flowing through the transistor 15.

  Similarly, a bias voltage 105 having a fixed value is applied to the base of the transistor 18, and a control voltage signal 107 is supplied to the base of the transistor 19 to control the value of the current flowing through the transistor 19. 19 can be adjusted, in other words, the ratio of the current flowing through the transistor 18 can be adjusted.

  Since the transistors 13, 15, and 16 operate as a grounded base circuit, the impedance of the transistor viewed from the emitter side is very small. For this reason, a voltage substantially equal to the input voltage signal 100b is applied to both ends of the resistor 10 and the capacitor 11 and converted into a current.

For example, the voltage value of the input voltage signal 100b is “Vi”, the resistance value of the resistor 10 is “R4”, the capacitance value of the capacitor 11 is “C5”, and the current flowing through the resistor 10 (hereinafter referred to as a low frequency component current). _Is “I _lf ” and the current flowing through the capacitor 11 (hereinafter referred to as a high-frequency component current) is “I _hf ”.
I _lf = Vi / R4 (3)
I _hf = Vi · jωC5 (4)
It becomes.

However, since the input current value adjusting means composed of the constant current source 12 and the transistor 13 is set so that the potential of the emitter of the transistor 13 is equal to the ground potential, the input voltage signal 100b is the ground voltage. The low frequency component current “I _lf ” flowing into the attenuation ratio adjusting means operates so that the current value becomes “0”.

Since the high frequency component current “I _hf ” flowing through the capacitor 11 flows into the constant current source 17, when the output current of the constant current source 17 is “I ₁₇ ”, the differential circuit composed of the transistors 15 and 16 includes The current “I ₁₇ −I _hf ” flows.

Therefore, when the ratio of the current flowing through the transistor 15 is “k1”, the current “k1 · (I ₁₇ −I _hf )” flows through the transistor 15.

On the other hand, the low frequency component current “I _lf ” flowing through the resistor 10 flows into the constant current source 20 via the transistor 13 to which the constant current source 12 is connected, so that the output current of the constant current source 12 is “I ₁₂ ”, When the output current of the constant current source 20 is “I ₂₀ ”, a current “I ₂₀ − (I ₁₂ + I _lf ) = I ₂₀ −I ₁₂ −I _lf is included in the differential circuit composed of the transistors 18 and 19. "Will flow.

Therefore, when the ratio of the current flowing through the transistor 18 is “k2”, the current “k2 · (I ₂₀ −I ₁₂ −I _lf )” flows through the transistor 18.

When the output current of the constant current source 14 is “k1 · I ₁₇ + k2 · (I ₂₀ −I ₁₂ )”, a current “k2 · I _lf + k1 · I _hf "will flow.

In other words, the current obtained by adding the low-frequency component current “I _lf ” and the high-frequency component current “I _hf ” by the coefficients “k2” and “k1” at a rate independent from each other of the capacitor 21 and the resistor 22 that are load circuits. It will flow to the parallel circuit.

Therefore, when the capacitance value of the capacitor 21 is “C6” and the resistance value of the resistor 22 is “R5”, the voltage value of the output voltage signal 101b is “Vo”.
Vo = R5 · (k2 · I _lf + k1 · I _hf )
/ (JωC6 ・ R5 + 1) (5)
It becomes.

And the damping ratio “Vo / Vi” is
Vo / Vi = R5 · (k2 · I _lf + k1 · I _hf )
/ Vi · (jωC6 · R5 + 1) (6)
And substituting Equation (3) and Equation (4) into Equation (6),
Vo / Vi = R5 · (k2 · Vi / R4 + k1 · Vi · jωC5)
/ Vi · (jωC6 · R5 + 1)
= R5 ・ (k2 / R4 + k1 ・ jωC5)
/ (JωC6 ・ R5 + 1)
= (K2 / R4 + k1 · jωC5)
/ (JωC6 + 1 / R5) (7)
It becomes.

At this time, the control voltage signals 106 and 107 are controlled so that “k2 · R5 / R4 = k1 · C5 / C6 = n” is satisfied, and the ratio “k1” of the current flowing through the transistor 15 and the current flowing through the transistor 18 are controlled. When the value of the ratio “k2” is adjusted, for example, in the case of a low frequency component, the real part of Equation (7) becomes dominant.
Vo / Vi = (k2 / R4) / (1 / R5)
= K2 / R5 / R4
= N (8)
It becomes.

On the other hand, in the case of a high frequency component, the imaginary part of Expression (7) becomes dominant,
Vo / Vi = (k1 · jωC5) / (jωC6)
= K1 ・ C5 / C6
= N (9)
Thus, the operation is performed with a constant attenuation ratio “n” regardless of the frequency of the input voltage signal 100b.

  As a result, the input voltage signal is converted into a low-frequency component current and a high-frequency component current by resistance and capacitance, and a current obtained by adding the low-frequency component current and the high-frequency component current in an independent ratio is supplied to the load circuit. The attenuation ratio can be adjusted with a simple circuit configuration.

In the embodiment shown in FIG. 1, the low-frequency component current flowing into the attenuation ratio adjusting means when the input voltage signal is the ground voltage using the input current value adjusting means comprising the constant current source 12 and the transistor 13 is used. The current value of “I _lf ” is set to “0”. However, when the input voltage signal is the ground voltage, the current value flowing into the attenuation ratio adjusting unit may be set to “0”.

  FIG. 2 is a block diagram showing the configuration of another embodiment of the attenuator according to the present invention. In FIG. 2, 10, 11, 14, 15, 16, 17, 18, 19, 20, 21, 22, 105, 106 and 107 are assigned the same reference numerals as in FIG. 1, 23 is a constant current source, and 100c. Is an input voltage signal, and 101c is an output voltage signal.

  Reference numeral 23 is an input current value adjusting means for the low frequency component current, and 14, 15, 16, 17, 18, 19 and 20 are attenuation ratio adjusting means.

  The input voltage signal 100c is applied to one end of the resistor 10, one end of the capacitor 11, and one end of the constant current source 23. The other end of the resistor 10 is connected to the emitters of the transistors 18 and 19 and one end of the constant current source 20, respectively. .

  The other end of the capacitor 11 is connected to the emitters of the transistors 15 and 16 and one end of the constant current source 17, respectively.

  One end of the constant current source 14 outputs the output voltage signal 101 c and is connected to the collectors of the transistors 15 and 18, one end of the capacitor 21, and one end of the resistor 22.

  Also, the bias voltage 105 is applied to the bases of the transistors 15 and 18, respectively, and the control voltage signals 106 and 107 are applied to the bases of the transistors 16 and 19, respectively.

  Further, the other ends of the constant current sources 14 and 23 and the collectors of the transistors 16 and 19 are connected to a positive voltage source, respectively, and the other ends of the constant current sources 17 and 20 are connected to a negative voltage source, respectively. The other end of the resistor 22 is grounded.

  Here, the operation of the embodiment shown in FIG. 2 will be described. However, the basic operation is almost the same as that of the embodiment shown in FIG. 1, and the description of the same operation as that of the embodiment shown in FIG.

  The output current value of the constant current source 3 is adjusted so that the current value flowing into the attenuation ratio adjusting means becomes “0” when the input voltage signal 100c is the ground voltage. Therefore, a circuit having an input current characteristic equivalent to that of the embodiment shown in FIG. 1 can be realized, and other operations are the same as those of the embodiment shown in FIG.

  In the embodiment shown in FIG. 1, the attenuation ratio is adjusted by the control voltage signals 106 and 107. However, it is of course possible to adjust by the control current signal instead of the control voltage signal.

  FIG. 3 is a block diagram showing the configuration of another embodiment of the attenuator according to the present invention. In FIG. 3, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 104, and 105 are assigned the same reference numerals as in FIG. 1, and 24 and 25 are currents. A resistor for performing voltage conversion, 100d is an input voltage signal, 101d is an output voltage signal, and 108 and 109 are control current signals.

  Reference numerals 12 and 13 constitute input current value adjusting means for low-frequency component currents, and 14, 15, 16, 17, 18, 19 and 20 constitute attenuation ratio adjusting means.

  The input voltage signal 100d is applied to one end of the resistor 10 and one end of the capacitor 11, and the other end of the resistor 10 is connected to one end of the constant current source 12 and the emitter of the transistor 13, respectively.

  The other end of the capacitor 11 is connected to the emitters of the transistors 15 and 16 and one end of the constant current source 17, respectively. The collector of the transistor 13 is connected to the emitters of the transistors 18 and 19 and one end of the constant current source 20, respectively.

  One end of the constant current source 14 outputs an output voltage signal 101 d and is connected to the collectors of the transistors 15 and 18, one end of the capacitor 21, and one end of the resistor 22.

  The bias voltage 104 is applied to the base of the transistor 13, and the bias voltage 105 is applied to the bases of the transistors 15 and 18 and one ends of the resistors 24 and 25, respectively.

  The control current signal 108 is applied to the base of the transistor 16 and the other end of the resistor 24, respectively, and the control current signal 109 is applied to the base of the transistor 19 and the other end of the resistor 25, respectively.

  Further, the other ends of the constant current sources 12 and 14 and the collectors of the transistors 16 and 19 are connected to a positive voltage source, respectively, and the other ends of the constant current sources 17 and 20 are connected to a negative voltage source, respectively. The other end of the resistor 22 is grounded.

  Here, the operation of the embodiment shown in FIG. 3 will be described. However, the basic operation is almost the same as that of the embodiment shown in FIG. 1, and the description of the same operation as that of the embodiment shown in FIG.

  The control current signals 108 and 109 applied to the attenuation ratio adjusting means are subjected to current-voltage conversion by the resistors 24 and 25, and the converted voltage is supplied to the bases of the transistors 16 and 19, thereby providing the embodiment shown in FIG. Adjust the damping ratio in the same way as

  1 and the like, the transistor 13 is a PNP transistor and the transistors 15, 16, 18 and 19 are NPN transistors. Of course, the transistor 13 is an NPN transistor, and the transistors 15, 16, 18 and 19 are PNP transistors. It does not matter.

  Further, the transistors 13, 15, 16, 18, and 19 may be MOS (Metal Oxide Semiconductor) transistors instead of bipolar transistors.

It is a block diagram showing a configuration of an embodiment of an attenuator according to the present invention. It is a block diagram which shows the other Example of the attenuator which concerns on this invention. It is a block diagram which shows the other Example of the attenuator which concerns on this invention. It is a structure circuit diagram which shows an example of the conventional attenuator. It is a structure circuit diagram which shows another example of the conventional attenuator.

Explanation of symbols

1, 5, 10, 22, 24, 25 Resistance 2, 6, 9, 11, 21 Capacity 3 Variable resistance 4 Variable capacity 7, 8 Variable gain amplifier circuit 13, 15, 16, 18, 19 Transistor 12, 14, 17 , 20, 23 Constant current source 100, 100a, 100b, 100c, 100d Input voltage signal 101, 101a, 101b, 101c, 101d Output voltage signal 102, 103 Gain control signal 104, 105 Bias voltage 106, 107 Control voltage signal 108, 109 Control current signal

Claims (6)

In an attenuator with adjustable attenuation ratio,
A resistor that converts the input voltage signal into a low frequency component current;
A capacity for converting the input voltage signal into a high-frequency component current;
A load circuit in which a resistor and a capacitor are connected in parallel;
Attenuation ratio adjusting means for supplying the load circuit with a current obtained by adding the low frequency component current and the high frequency component current in an independent ratio;
An attenuator comprising input current value adjusting means for adjusting a current value of the low frequency component current flowing into the attenuation ratio adjusting means. In an attenuator with adjustable attenuation ratio,
A resistor that converts the input voltage signal into a low frequency component current;
A capacity for converting the input voltage signal into a high-frequency component current;
A load circuit in which a resistor and a capacitor are connected in parallel;
Attenuation ratio adjusting means for supplying the load circuit with a current obtained by adding the low frequency component current and the high frequency component current in an independent ratio;
An attenuator comprising an input current value adjusting means for adjusting a current value flowing into the attenuation ratio adjusting means. The damping ratio adjusting means is
First and second constant current sources;
A first differential circuit in which the low frequency component current is supplied to each emitter and connected to the first constant current source, and a control voltage signal of the low frequency component current is applied to the base of one transistor;
A second differential circuit in which the high-frequency component current is supplied to each emitter and connected to the second constant current source, and a control voltage signal of the high-frequency component current is applied to the base of one transistor;
The third constant current source for supplying the added current to the load circuit, to which the collectors of the other transistors of the first and second differential circuits are respectively connected. The attenuator according to claim 1 or 2. The damping ratio adjusting means is
First and second constant current sources;
The low-frequency component current is supplied to each emitter, the first constant current source is connected, and the control current signal of the low-frequency component current is voltage-converted and applied to the base of one transistor. Dynamic circuit,
A second differential circuit in which the high-frequency component current is supplied to each emitter, the second constant current source is connected, and the control current signal of the high-frequency component current is voltage-converted and applied to the base of one transistor. When,
The third constant current source for supplying the added current to the load circuit, to which the collectors of the other transistors of the first and second differential circuits are respectively connected. The attenuator according to claim 1 or 2. The input current value adjusting means is
A constant current source;
One end of the resistor for converting an input voltage signal into a low-frequency component current and the constant current source are connected to the emitter, and the emitter is configured to have a potential equal to the ground potential. The attenuator according to claim 1. The input current value adjusting means is
The constant voltage source is connected to one end of the resistor for converting an input voltage signal into a low frequency component current and sets a current value flowing into the attenuation ratio adjusting means to 0 when the input voltage signal is a ground voltage. The attenuator according to claim 2.

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